Infiltration glass containing niobium

ABSTRACT

The present invention relates to an all-ceramic dental prosthesis in which a porous ceramic matrix material is infiltrated with a glass, having a solubility of &lt;1100 μg/cm 2  according to DIN EN ISO 6872. The invention also relates to the use of niobium-containing glass having an Nb 2 O 5  content of more than 0.1% by weight as an infiltration glass for all-ceramic dental compositions.

The present invention relates to a niobium-containing infiltration glass, especially for ceramic bodies, and a ceramic body employable as an all-ceramic dental prosthesis in which a porous ceramic matrix material is infiltrated with a glass.

Today, all-ceramic compositions are employed in the frontal tooth region, as inlays, onlays, veneers and posterior fixed partial dentures.

EP-B-0 241 384 describes a process in which metal oxide particles are sintered with open pores, and the infrastructure thus obtained is subsequently infiltrated with a glass. The sintered infrastructure mainly consists of alumina and/or zirconia. An alkaline borosilicate glass containing alumina is described as an infiltration glass. In the Examples, lanthanum oxide is one of the main components of the glass. The expansion coefficient is to be slightly below that of the porous infrastructure.

DE-B-100 61 630 discloses a process in which cerium-stabilized zirconia and mixtures of cerium-stabilized zirconia with alumina are used as a matrix material. In addition, a glass having a composition of 15-35% by weight La₂O₃, 10-25% by weight SiO₂, 10-25% by weight Al₂O₃, 5-20% by weight B₂O₃, 5-20% by weight CaO, 0-10% by weight ZrO₂, 0-10% by weight TiO₂ and 0-15% by weight CeO₂ is claimed, as well as additions of further ZrO₂-stabilizing metal oxides, especially 0-10% by weight MgO and 0-10% by weight Y₂O₃.

Further, DE 692-T-06 256 describes matrix materials based on alumina/magnesia spinels.

WO-A-2005/115936 relates to a glass or glass ceramic powder comprising multicomponent glasses with at least three elements characterized in that the glass or glass ceramic powder has a mean particle size of <1 μm, preferably <0.1 μm, more preferably <10 nm. Disclosed are glass compositions of 5% by weight SiO₂, 20% by weight B₂O₃, 2.5% by weight TiO₂, 2.5% by weight ZrO₂, 20% by weight ZnO, 35% by weight La₂O₃, 5% by weight WO₃ and 10% by weight Nb₂O₅, designed for use in the field of infiltration glasses and dental ceramics. In Computational Modelling of Materials, Minerals and Metals Processing, edited by M. Cross, J. W. Evans and C. Bailey, TMS (The Minerals, Metals & Materials Society), 2001, Anil Saigal et al. describe infiltration glasses of La₂O₃—Al₂O₃—B₂O₃—SiO₂ in which niobium is not contained.

It is the object of the invention to develop a glass that can be infiltrated into the known all-ceramic matrices and has improved mechanical and chemical stabilities. The glasses employed to date are limited by various boundary conditions. The infiltration temperature must be below the sintering temperature of the matrix, best below 1200° C. The expansion coefficient must be slightly below that of the matrix. The glass must not have an undesirable color. It must be possible to infiltrate the glass flawlessly. The glass is to have high mechanical and chemical stabilities. It is especially the limitation of the infiltration temperature and thus the viscosity of the glass-forming melt that conflicts with the chemical and mechanical stability, since glasses having a high proportion of network formers (e.g., SiO₂, B₂O₃) have very good mechanical and chemical stabilities, but reach the required viscosity of about 10³ dPas only at elevated temperatures.

Although the high lanthanum glass used to date can be filtrated excellently and exhibits good mechanical properties when exactly matched in terms of expansion behavior, it is sufficient only as a matrix material in the field of chemical stability within the meaning of dental standards.

Surprisingly, it has been found that the use of niobium oxide both as an additive to lanthanum-containing glasses and as a component in other silicate systems provokes a significant improvement in chemical stability. The object of the invention is achieved by a silicate-based infiltration glass for ceramic bodies wherein said infiltration glass contains niobium in greater than naturally occurring quantities. In the infiltration glasses according to the invention, the Nb may occur in amounts of at least 0.1% by weight, calculated as Nb₂O₅ and based on the total amount of the infiltration glass. In particular, the system SiO₂—Nb₂O₅—Na₂O/K₂O, for example, can have from 10 to 70% by weight SiO₂, from 1 to 40% by weight Na₂O/K₂O and from 1 to 60% by weight Nb₂O₅.

The infiltration glass according to the invention showed a reduction in glass solubility to below 3% of that of the known glasses when aged as a defined glass grit (grain fraction 100-200 μm, by analogy with DIN ISO 719) in 4% acetic acid at 80° C. for 16 hours. The mechanical properties and the further specifications are not adversely affected by the niobium oxide. In particular, the infiltration glass according to the invention has a solubility of <1100 μg/cm², especially <900 μg/cm² or <700 μg/cm² according to DIN EN ISO 6872.

In one embodiment of the invention, the infiltration glass according to the invention contains additions of matrix components, especially Al₂O₃, CeO₂, Y₂O₃ and/or ZrO₂.

In another embodiment, the infiltration glass according to the invention from the system SiO₂-La₂O₃—Al₂O₃—B₂O₃ with 15-35% by weight La₂O₃, 10-25% by weight SiO₂, 10-25% by weight Al₂O₃, 5-20% by weight B₂O₃, 5-20% by weight CaO, 0-10% by weight ZrO₂, 0-10% by weight TiO₂ and 0-15% by weight CeO₂ additionally contains Nb₂O₅ in an amount of from 0.1 to 20% by weight.

The infiltration glass according to the invention may contain further metal oxides at an oxidation stage suitable for the stabilization of ZrO₂, wherein 0-10% by weight MgO and/or 0-10% by weight Y₂O₃ may be admixed, in particular.

The infiltration glass according to the invention may further contain coloring oxides.

The infiltration glass according to the invention may typically be prepared and sold as a powder.

Then, the powder can be used, for example, for the infiltration of porous ceramic bodies in a per se known manner. Thus, the invention also relates to ceramic bodies infiltrated with the infiltration glass according to the invention, for example, dental restorations.

Further, the invention also relates to the use of niobium-containing glass having an Nb₂O₅ content of more than 0.1% by weight as an infiltration glass for all-ceramic dental compositions. In particular, Nb₂O₅ may be present in the infiltration glass according to the invention in amounts of from 0.1 to 20% by weight or from 5 to 15% by weight.

EXAMPLES Example 1

A glass from the SiO₂—Nb₂O₅—Na₂O—B₂O₃ system with additions of alumina, zirconia and ceria for use for matrices of alumina and cerium-stabilized zirconia, so that no remarkable dissolution or deposition processes from the matrix into the glass or from the glass occur.

The glass with a composition of 29.5% by weight SiO₂, 28.7% by weight Nb₂O₅, 12.8% by weight Na₂O, 6.8% by weight B₂O₃, 8.0% by weight Al₂O₃, 6.6% by weight ZrO₂ and 7.6% by weight CeO₂ exhibits a weight loss of 3.5 mg per gram of substance after 16 hours when aged in 4% acetic acid at 80° C. The expansion coefficient α₂₀₋₃₀₀ is 8.3·10⁻⁶ K⁻¹, matched to a matrix of 50% by weight cerium-stabilized zirconia and 50% by weight alumina. The infiltration glass for dental all-ceramics that is employed most frequently currently (In Ceram© zirconia glass) has a weight loss of about 120 mg/g of substance.

Example 2

The glass with a composition of 29.9% by weight SiO₂, 37.0% by weight Nb₂O₅, 11.1% by weight Na₂O, 7.5% by weight K₂O, 6.7% by weight ZrO₂ and 7.7% by weight CeO₂ exhibits a weight loss of 9.2 mg per gram of substance after 16 hours when aged in 4% acetic acid at 80° C. The expansion coefficient α₂₀₋₃₀₀ is 9.3·10⁻⁶ K⁻¹, in this case matched to a pure cerium-stabilized zirconia matrix.

Example 3

The glass with a composition of 21.5% by weight SiO₂, 11.0% by weight B₂O₃, 17.5% by weight Al₂O₃, 5.5% by weight CaO, 31% by weight La₂O₃, 4% by weight TiO₂, 9.5% by weight Nb₂O₅ exhibits a chemical solubility of 653 μg/cm² according to DIN EN ISO 6872 after infiltration into a VITA© In-Ceram Classic ALUMINA BLANK©. In comparison, the previously commercially available VITA In-Ceram© ALUMINA GLASS POWDER exhibits a chemical solubility of about 1200 μg/cm². 

1.-13. (canceled)
 14. An infiltration glass with niobium in quantities greater than naturally occurring quantities comprising a SiO₂—Nb₂O₅—Na₂O/K₂O system with from 10 to 70% by weight SiO₂, from 1 to 60% by weight Nb₂O₅, and from 1 to 40% by weight Na₂O/K₂O, with the weight percentage being based on the total amount of the infiltration glass.
 15. The infiltration glass according to claim 14 further comprising Al₂O₃, CeO₂, Y₂O₃, ZrO₂, or a combination thereof.
 16. The infiltration glass according claim 14, wherein said infiltration glass further comprises metal oxides at an oxidation stage suitable for the stabilization of ZrO₂.
 17. The infiltration glass according to claim 14, wherein said infiltration glass comprises from 0 to 10% by weight MgO and/or from 0 to 10% by weight Y₂O₃.
 18. The infiltration glass according to claim 14 wherein said infiltration glass comprises coloring oxides.
 19. The infiltration glass according to claim 14 having a solubility of <1100 μg/cm² according to DIN EN ISO
 6872. 20. A ceramic body obtainable by infiltration of a porous ceramic body with an infiltration glass according claim
 14. 21. The ceramic body according to claim 20, characterized in that said ceramic body is a dental restoration.
 22. A method of treating a ceramic body comprising infiltrating the ceramic body with an infiltration glass that comprises a SiO₂—Nb₂O₅—Na₂O/K₂O system with from 10 to 70% by weight SiO₂, from 1 to 60% by weight Nb₂O₅, and from 1 to 40% by weight Na₂O/K₂O, with the weight percentage being based on the total amount of the infiltration glass.
 23. The method of claim 22 wherein the ceramic body infused with the infiltration glass provides an all-ceramic dental composition.
 24. An infiltration glass with niobium in quantities greater than naturally occurring quantities comprising an addition of Nb₂O₅ of from 0.1 to 20% by weight to the system SiO₂—La₂O₃—Al₂O₃—B₂O₃ with 15-35% by weight La₂O₃, 10-25% by weight SiO₂, 10-25% by weight Al₂O₃, 5-20% by weight B₂O₃, 5-20% by weight CaO, 0-10% by weight ZrO₂, 0-10% by weight TiO₂ and 0-15% by weight CeO₂.
 25. The infiltration glass according claim 24, wherein said infiltration glass further comprises metal oxides at an oxidation stage suitable for the stabilization of ZrO₂.
 26. The infiltration glass according to claim 24, wherein said infiltration glass comprises from 0 to 10% by weight MgO and/or from 0 to 10% by weight Y₂O₃.
 27. The infiltration glass according to claim 24 wherein said infiltration glass comprises coloring oxides.
 28. The infiltration glass according to claim 24 having a solubility of <1100 μg/cm² according to DIN EN ISO
 6872. 29. A ceramic body obtainable by infiltration of a porous ceramic body with an infiltration glass according claim
 24. 30. The ceramic body according to claim 29, characterized in that said ceramic body is a dental restoration.
 31. A method of treating a ceramic body comprising infiltrating the ceramic body with an infiltration glass that comprises niobium in quantities greater than naturally occurring quantities comprising an addition of Nb₂O₅ of from 0.1 to 20% by weight to the system SiO₂—La₂O₃—Al₂O₃—B₂O₃ with 15-35% by weight La₂O₃, 10-25% by weight SiO₂, 10-25% by weight Al₂O₃, 5-20% by weight B₂O₃, 5-20% by weight CaO, 0-10% by weight ZrO₂, 0-10% by weight TiO₂ and 0-15% by weight CeO₂.
 32. The method of claim 31 wherein the ceramic body infused with the infiltration glass provides an all-ceramic dental composition. 